The present disclosure relates generally to memory circuits, and more particularly, to a control circuit for performing inhibit operations during the writing of a memory cell by implementing pre-defined biased controls and self-latch features.
In the new age of technology, flash memory has turned into one of the most popular read-only memory (ROM) available in the market mainly because of its capability of allowing easy and fast permanent data storage for devices such as computers, digital cameras, and many other portable devices. While other storage methods such as hard drive and random-access memory (RAM) are still used, flash memory remains as a competitive choice. Flash memory is considered a solid state device that provides users with a quicker and more reliable way of storage. Flash memory also allows users to write data into the memory cells permanently—a feature that the random-access memory (RAM) does not provide.
However, with all these advantages, flash memory still has its tradeoffs. The writing of data to flash memory can be a long process, since the process typically requires a much higher voltage and current than the writing process of random-access memory (RAM). In order to write to flash memory cells, source lines are biased with high voltage, and the selected memory cell must reach the effective program current, which would be the difference between the biased pull-down NMOS current and controlled pull-up PMOS current that charges the bit lines. However, a leakage current can occur after each programming and erasing cycle while the current travels through the bit lines, thereby lowering the effective program current that is needed to write to the memory cells. One conventional method to solve this problem is to simply make the controlled pull-up PMOS current large enough so the leakage current would not affect the writing process. However, by increasing the controlled pull-up PMOS current, controlling the effective program current within in a certain range required for the memory cells becomes difficult.
Desirable in the art of memory modules, such as flash memory, are additional designs that solve current leakage issues while providing better control over the effective program current during the writing process.